1. Field of the Invention
This invention relates to computer systems and, more particularly, to apparatus for providing electrical connections used between layers of very high density hybrid electronic circuits.
2. History of the Prior Art
The semiconductor and other devices utilized in modern computer systems function correctly only when operating within specified temperature ranges. In general, the components are designed to operate reliably within a relatively narrow range which may extend to about 110 degrees C. at the upper limit. Above this point, the devices themselves are unreliable in handling digital information and may well be destroyed as the temperature rises. Typically, desktop computer systems such as personal computers and work stations include a motherboard upon which are positioned a central processing unit, memory, and input/output circuitry connected to a system bus. Slot connections are provided to the system bus on the motherboard for system peripheral components. Ambient air, often driven by small fans installed within the case of the computer, is usually sufficient to cool the electronic circuitry to appropriate operating temperatures.
An entirely different packaging arrangement which is the subject of copending patent application Ser. No. 07/553,521, entitled Three Dimensional Packaging Arrangement for Computer Systems and the Like, filed July 13, 1990, H. Davidson, allows a very powerful computer (e.g., one with up to 0.5 gigabytes of random access storage and as many as four individual processors) to be contained in a volume approximately four inches on a side and one inch thick. Such a compact arrangement is obtained by placing very thin layers of hybrid circuits, essentially against one another to form a total computer package. Such a powerful computer is capable of operating at faster speeds than conventionally-packaged computers because the short lengths of conductors used for buses substantially reduce impedances. However, the higher packing densities of these arrangements have tended to raise the operating temperatures to levels which normal ambient air cooling cannot handle.
For example, in order to obtain very fast operating speeds from such a computer, very high speed devices may be used in the embedded chips. These devices require a great deal of power and produce very high operating temperatures. With such a system, as much as two hundred amperes of current may be utilized at each layer of electronic devices, producing as much as one thousand watts of power at each of a number of the layers of the arrangement. Prior art cooling techniques will simply not keep a computer of this sort within the operating temperature limits of its electronic devices, and the apparatus will be destroyed within a very short time after power is applied.
In order to remove the heat from such arrangements in higher power uses, a novel arrangement of heat exchange units has been devised. Such an arrangement is disclosed in U.S. patent application Ser. No. 07/553,541, entitled Apparatus For Cooling Compact Arrays Of Electronic Circuitry, H. Davidson, filed July 13, 1990. Basically, the heat exchange units comprise at least one heat-removing layer positioned between and against at least one of the layers carrying electronic devices. The heat-removing layers are arranged with an interior channel for transferring a fluid to accomplish the heat removal. Tests have shown that such a heat exchanger is capable of cooling a single layer of circuitry consuming more than five hundred watts of power to approximately 47 degrees C. at the surface of the heat exchanger.
Such arrangements work well in situations in which the conductors electrically connecting the layers of electronic circuitry are routed through ceramic and other non-conductive insulators which provide structural positioning for all of the layers. However, the number of conductors necessary to such circuitry tends to proliferate in very powerful computers. Consequently, structural arrangements for providing electrical conduits between layers are drastically limited in high powered computers requiring the use of heat removal devices such as those disclosed in the last above-mentioned patent application.